This invention relates to hauling systems, and more specifically to systems for hauling loose bulk material at a construction site using a self-propelled vehicle ordinarily found on the site and a drawn trailer.
At almost every construction site it is necessary to move construction materials, gravel, dirt, and like loose bulk material. Currently at most construction sites special hauling vehicles, such as self-propelled dump trucks, are used in excavation to complement a front wheel loader or steam shovel that lifts and loads dirt and debris into the truck. These solutions work well, but require the extra capital and operating costs of the dump truck and its driver in addition to the wheel loader or steam shovel and its operator.
While in general a wide variety of hauling systems are well known, such as railroad trains, light pickup trucks, tractor trailer trucks, and sophisticated refuse pick up and hauling trucks, most are not suited to use at a construction site. Railroads require rails. Few construction projects warrant the construction of special rail lines. Ordinary highway vehicles are built to haul loads for long distances over comparatively smooth, hard-surfaced highways. The suspensions, trailer attachment arrangements, weight distribution and general ruggedness of highway tractor-trailers are not well suited to the harsh and uneven terrain of a construction site. Pickup trucks are not sufficiently rugged and do not have the necessary carrying capacity for construction site hauling. Hence the frequent use of self-propelled, heavy-duty dump trucks and dumpsters, despite their cost and other drawbacks.
In hauling systems involving a self-propelled vehicle (a "tractor") and a drawn (non self-propelled) trailer, the tractor and the trailer must connect and disconnect, and ideally should do so reliably and with relative ease. In existing hauling systems, it is sometimes necessary for the operator of the tractor to rely on an observer to direct the tractor into alignment with the trailer so that the two vehicles can be connected. Even where some form of alignment mechanism visible from the cab of the tractor permits the operator to align the vehicles alone, as in U.S. Pat. No. 4,313,264 to Miller; U.S. Pat. No. 4,723,788 to Suter; or U.S. Pat. No. 4,666,176 to Sand, it is generally necessary for the operator to exit from the tractor in order to physically connect the tractor to the trailer. In those systems that permit the vehicles to be connected without the operator exiting from the tractor, e.g. U.S. Pat. No. 4,560,183 to Cook, the operator must still exit from the tractor to dismantle the connecting mechanism once the vehicles are connected. This is necessary in order to permit complete freedom of movement of the tractor and trailer in combination.
Another deficiency in existing hauling systems, such as the one described in Cook, is that they will not function if the rear of the tractor and front of the trailer are out of vertical alignment. While this may be a manageable problem for conventional highway vehicles that are assembled on comparatively flat, hard surfaces such as concrete or asphalt parking areas, it is a more difficult problem when tractor and trailer are to be coupled on uneven, varying terrain such as usually found on a construction site. This problem is accentuated where the trailer can tip over, as is usually the case with a drawn trailer when it is usually designed to have a net downward force at the front end of the trailer during travel. Weight distribution even further accelerates the problem. Where a heavy load is added in batches or where the center of gravity of the loaded vehicle can vary greatly depending on the weight distribution of the load, the force acting on a "land" or jack or the like under the front end of the trailer to hold it horizontal when at rest and detached can vary greatly. If the ground is not paved or otherwise very firm, the weight of the load can cause one end of the trailer to sink into the ground as the trailer is loaded, or to sink in over time once it is loaded. A viable trailer hauling system for a construction site must therefore deal with variation in the height of the trailer-to-tractor connection and changes in the height during use.
In other existing systems, such as that described in U.S. Pat. No. 4,133,552 to Sheine, in addition to requiring an operator to leave the tractor, the mechanism that permits the two vehicles to be connected requires extensive connections between the two vehicles that must be completed by the operator who leaves the cab of one vehicle, or a second individual. This is inconvenient and inefficient if the vehicles are to be connected and disconnected frequently, not to mention safety concerns to the operators moving around the site and working with heavily loaded equipment in a hazardous, uneven environment.
A further concern is that the vehicle carrying the load must be readily unloaded. The usual approach is to dump the load over an end wall of a dump body or through a hinged gate or flap mounted as or at the rear end wall. In the standard dump truck, hydraulic jacking one end of a load-carrying body slides the load out of a pivoted gate or over the end of a load-carrying body. In a conventional dump truck, the truck motor can power a hydraulic jack for the dumping operations. Highway tractor trailers with a dumping capability are known, but they are not well suited to operation at a construction site. They have a large turn radius, and they are comparatively long and narrow which makes them unstable on construction site terrain. It is therefore highly desirable to be able not only to readily connect a drawn trailer to a self-propelled vehicle without a second operation and with a secure connection during travel, but also to dump the load after travel and to do so with a minimum of extra capital cost.
It is therefore a principal object of this invention to provide a hauling system in which the usual functions of two separate vehicles, one to load and the other to haul and dump, are accomplished by a single operator.
It is also a principal object of this invention to provide a hauling system where a single operator connects and disconnects two vehicles without leaving the operating cab of one vehicle to align, connect, load, dump, or disconnect the second vehicle.
Another principal object of this invention is to provide a hauling system which uses a slightly modified self-propelled vehicle ordinarily found on a construction site as a propelling vehicle for the hauling thereby saving the capital and operating cost of two self-propelled vehicles.
Another object of this invention is to provide a hauling system with the foregoing advantages which allows a rapid and reliable connection of the trailer despite variations in the position of the connection due to the load, load shifts, variations in the terrain, or the sinking of one or both vehicles into the terrain.
A further object is to provide these advantages while also providing a dumping capability to unload a trailer, even where a load-carrying dump body is fixed on a trailer frame.
Yet another object of this invention is to provide a two-vehicle, one-operator hauling system in which two vehicles can be connected to one another and their operation controlled without electrical, hydraulic, or pneumatic lines connected between the vehicles.